If you have problems using SCP, SFTP, rsync, or other commands trying to connect to or from a remote server to your Centmin Mod server, you will need to whitelist the remote server's IP address as per above command. Common, situation would be connecting to a remote MySQL server which you need to whitelist remote MySQL server IP address as well as edit /etc/csf/csf.conf to add to TCP_OUT the default MySQL port 3306. Then restart CSF firewall service.

If you use third party SMTP services, you also need to add the appropriate ports toTCP_OUT listing within /etc/csf/csf.conf. Then restart CSF firewall service.

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most common is TCP_OUT port 587 needs adding or whatever you using to connect to Mandrill